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Write a program which reads a sequence A of n elements and an integer M, and outputs "yes" if you can make M by adding elements in A, otherwise "no". You can use an element only once.
You are given the sequence A and q questions where each question contains Mi.
In the first line n is given. In the second line, n integers are given. In the third line q is given. Then, in the fourth line, q integers (Mi) are given.
For each question Mi, print yes or no.
51 5 7 10 2182 4 17 8 22 21 100 35
nonoyesyesyesyesnono
You can solve this problem by a Burte Force approach. Suppose solve(p, t) is a function which checkes whether you can make t by selecting elements after p-th element (inclusive). Then you can recursively call the following functions:
solve(0, M)
solve(1, M-{sum created from elements before 1st element}) solve(2, M-{sum created from elements before 2nd element}) ...The recursive function has two choices: you selected p-th element and not. So, you can check solve(p+1, t-A[p]) and solve(p+1, t) in solve(p, t) to check the all combinations.
For example, the following figure shows that 8 can be made by A[0] + A[2].
代码如下:
#include#include #include #include using namespace std;const int maxn=25;int n,q;int a[maxn];int flag;int x;void cho (int loc,int sum){ if(sum==x) { flag=1; return; } if(loc>n) return; cho (loc+1,sum); cho (loc+1,sum+a[loc]);}void input (){ scanf("%d",&n); for (int i=1;i<=n;i++) scanf("%d",&a[i]); scanf("%d",&q); while (q--) { scanf("%d",&x); flag=0; cho (1,0); if(flag) printf("yes\n"); else printf("no\n"); }}int main(){ input(); return 0;}
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